With the fsb at 309 you're running at ~2.47GHz, 340 (2.72GHz) is going to be around the limit of what you'll get I should think. Give it a go though.
As long as your temps don't go any higher than 70/80C under load using something like IBT then you're fine. If the system crashed or fails to boot then lower the FSB slightly.
cool how do you work out the Ghz from the fsb?